The inclusion and maintenance of high flavor levels in chewing gum has long been a problem. Where it has been attempted to include flavors at a level in excess of 1.5%, it has been found that the increased flavor render the chewing gum excessively soft, sticky and difficult to handle in normal manufacturing processing.
U.S. Pat. No. 3,894,154 to Graff et al discloses a liquid center-filled chewing gum which includes a water-miscible humectant, such as glycerin, to maintain the fluidity of the liquid center. The use of the glycerin vehicle also allows for the inclusion of increased flavor levels within the liquid center, but does not inhibit migration of flavor into the chewing gum at the liquid/gum interface which occurs within a relatively short period of time after manufacture.
British Patent Application 2,016,895A discloses that the flavor migration problem discussed above may be resolved by including a mixture of sorbitol and proylene glycol in the liquid filling.
U.S. Pat. No. 1,198,423 to Pryor discloses a chewing gum which may be formed of a tube of chewing gum having a flavor stick core arranged within the central bore of the tube. Pryor indicates that the core may be a gum of concentrated flavor, that is, a casing of gum which itself may be flavored and a central flavor vehicle, such as a sugar preparation, which will carry a more concentrated flavor than can be imparted to a gum. The tube of chewing gum would be of neutral flavor so as to dilute the flavor of the core. In effect, Pryor teaches surrounding a sugar candy core with a gum casing, and then inserting the resulting combination in a tube of chewing gum. The chewing gum in either the casing or the tube would not include inordinate amounts of flavor due to the manufacturing and packing problems discussed above.
Accordingly, a need still exists for a solid center-filled chewing gum which center portion includes substantial amounts of flavor which will be retained in the center portion and not migrate to the outer shell portion of the gum and yet be capable of being manufactured and packaged using standard equipment.